JPH11194010A - Position sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce crosstalk when sensing a small position by a reflection-type hotosensor and a reflection plate where a reflection pattern is formed. SOLUTION: A reflection plate 5 is mainly mounted on a moving body that travels in an X direction and a reflection type photosensor is mounted on a fixed body. A reflection pattern where a reflection surface 10A and a non- reflection surface in a thin band shape extended in a Y direction are alternately arranged in an X direction is formed. By gradually increasing or decreasing the width in the X direction of the reflection surface 10A and the non-reflection surface 10B according to their arrangement position, the quantity of light returning to the photosensor is changed according to a reflection position and the position in the X direction can be determined. Then, by gradually decreasing the width in the X direction of each reflection surface near the edge in the direction of Y of the reflection plate 5 toward the edge from the center in the Y direction, it is canceled out by the increase in the quantity of reflection light near an edge due to irregular reflection, thus stabilizing output fluctuation in the case of the displacement in the Y direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for detecting the position of a movable body using a reflection type photo sensor.

[0002]

2. Description of the Related Art As shown in FIG. 6, a conventional position detecting device of this type has a movable body 113 which moves mainly in the X direction among the X and Y directions orthogonal to each other, and has a position in an XY plane. A reflector 112 is attached, and a fixed body 114 facing the reflector 112 is irradiated with a light beam (hereinafter also referred to as a sensor beam) 116 on the reflector 112 to receive return light from the reflector 112. A reflection type photosensor 115 for generating an output corresponding to the return light is attached, and a reflection plate 112 is formed by alternately arranging, in the X direction, narrow band-shaped reflection surfaces 111A and non-reflection surfaces 111B each extending in the Y direction on the reflection plate 112. A pattern is formed, and the reflection surface 11 of the reflection pattern is formed.
By gradually increasing and decreasing the X-direction width of the non-reflective surface 1A and the non-reflective surface 111B at a constant rate,
5, the position of the movable body 113 in the X direction is detected based on a change in the output of the photosensor 115 based on the change in the amount of light returning.

[0003] In this case, as shown in FIG.
11A has a constant width in the X direction from the center to the edge in the Y direction. Even if a slight displacement in the Y direction occurs, the output of the photosensor 115 does not fluctuate unless there is a displacement in the X direction. It does not appear, so that the displacement of the movable body 113 in the X direction can be detected.

[0004]

By the way, in the conventional position detecting device, when the movable body 113 is displaced in the Y direction and the sensor beam 116 approaches the edge (edge) of the reflecting plate 112, the reflecting plate 112 is displaced. Even if there is no displacement in the X direction due to the irregular reflection of the edge portion of the sensor, the sensor output fluctuates, and this causes crosstalk, so that accurate X
There is a problem that the direction position cannot be detected. In particular, when it is difficult to secure the dimension of the reflection plate 112 in the Y direction due to space constraints, the problem is likely to occur. If any displacement in the Y direction occurs, stable position detection cannot be performed. Was. FIG. 8 shows the movable body 113.
4 shows the relationship between the displacement in the Y direction and the output of the photosensor 115.

The present invention has been made in view of the above circumstances, and has as its object to provide a position detecting device capable of performing stable position detection even when a displacement occurs in a direction orthogonal to the moving direction of a movable body.

[0006]

In order to achieve the above object, the present invention is directed to a movable member which moves mainly in the X direction among the X and Y directions orthogonal to each other, and is provided with a position in the XY plane. Attaching a reflection plate, and mounting a photosensor that generates an output according to the return light by irradiating light to the reflection plate and receiving return light from the reflection plate on the fixed body facing the reflection plate, The reflection plate is formed with a reflection pattern in which thin strip-shaped reflection surfaces and non-reflection surfaces each extending in the Y direction are alternately arranged in the X direction, and the X-direction widths of the reflection surfaces and the non-reflection surfaces of the reflection patterns are set to be equal to each other. A position detecting device that changes the amount of light returning to the photosensor in accordance with the reflection position by gradually increasing or decreasing the position in accordance with the array position, and detects the position of the movable body in the X direction based on a change in the output of the photosensor based on this. In the above The X-direction width of each of the reflective surfaces at the edges near the Y direction radiation plate, characterized in that gradually increase or decrease toward the edge from Y direction center.

According to a second aspect of the present invention, in the first aspect, the width in the X direction of each of the reflecting surfaces is made constant in a predetermined range at the center in the Y direction, and is increased or decreased near both end edges outside the predetermined range. It is characterized by.

According to a third aspect of the present invention, in the first or second aspect, the increase / decrease ratio of the width in the X direction in the vicinity of the edge in the Y direction of each of the reflecting surfaces is determined by the output of the photosensor with respect to the vicinity of the edge in the Y direction of the reflecting surface. Are set so as to be substantially equal to the output of the photosensor with respect to the center of the reflection surface in the Y direction.

In this type of position detecting device, a beam emitted from a photosensor installed at a position facing the reflector is applied to a reflection pattern on the reflector, and return light from the reflector is reflected by the photosensor. Received. When the movable body is displaced, the reflection pattern on the reflection plate is also displaced, and the position of the reflection pattern irradiated by the beam also changes. If the direction of displacement of the movable body is only the Y direction, the ratio of the reflection surface occupying the irradiation beam area does not change and the sensor output does not change. However, depending on the finished state of the edge portion of the reflection plate, irregular reflection occurs at this portion. Occurs, the reflected light more than necessary is incident on the photosensor, and the output of the photosensor fluctuates despite no displacement in the X direction.

In this regard, in the position detecting device of the present invention, the reflection pattern near the edge of the reflection plate is gradually reduced in the X direction so that the reflection area is reduced in advance, so that the reflection plate is Y-shaped. When the sensor beam is displaced in the direction, the decrease in the reflected light due to the decrease in the reflection surface and the increase in the reflected light due to the irregular reflection of the reflector edge cancel each other, and as a result, even if the sensor beam comes off the reflector, the output is stable to some extent. Can be kept. Conversely, when the reflected light decreases at the edge of the reflector and the sensor output decreases, the reflection pattern near the edge of the reflector is gradually increased in the X direction so that the reflection area increases. Keep increasing. By doing so, the increase in reflected light due to the increase in the reflection surface and the decrease in reflected light due to the influence of the edge of the reflector cancel each other out, and a stable sensor output can be obtained.

That is, by gradually increasing or decreasing the width of each reflecting surface in the X direction from the center toward the edge in the Y direction, unnecessary output fluctuations when the movable body is moved in the Y direction are reduced, and the movable body is stabilized. It enables X-direction displacement detection. Specifically, when the sensor output increases when the sensor beam is irradiated near the edge of the reflecting plate due to the movement of the movable body in the Y direction, the width of the reflecting surface in the X direction is gradually reduced. Is decreased, the width of the reflecting surface in the X direction is gradually increased. As a result, unnecessary output fluctuation due to movement in the Y direction is prevented from occurring.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. In this embodiment, an example is described in which the amount of reflected light input to the photosensor increases at an edge portion (edge portion) in the Y direction of the reflector.

FIG. 1 is a perspective view schematically showing the overall configuration of the position detecting device, and FIG. 2 is a configuration diagram of a reflection pattern in the device of FIG. As shown in FIG. 1, in this position detection device, a reflecting plate 5 located in the XY plane is attached to a movable body 6 that moves mainly in the X direction among the X and Y directions orthogonal to each other. In the fixed body 8 facing the reflection plate 5,
A reflection-type photosensor 7 that irradiates a sensor beam 9 to the reflection plate 5 and receives return light from the reflection plate 5 to generate an output according to the return light is attached. Reflector 5 has
A strip-shaped reflective surface 10A and a non-reflective surface 1 each extending in the Y direction
0B are alternately arranged in the X direction to form a reflection pattern.

In order to form a reflection pattern, first, as shown in FIG.
It is divided into blocks of width A (for example, 0.12 mm). In this block of width A, one strip-like reflecting surface 10A
And one non-reflective surface 10B are arranged in pairs, and the width A
The width of the reflecting surface 10A is changed for each of the blocks so that the reflecting surface 10A increases and decreases at a constant rate as the entire reflecting pattern. For example, from the right block to the left block in FIG.
m, 0.060mm, 0.065mm,
Non-reflective surface 1
0B is correspondingly reduced. Then, as described above, the X of the reflection surface 10A and the non-reflection surface 10B of the reflection pattern
By gradually increasing or decreasing the direction width at a fixed rate, the amount of light returning to the photosensor 7 in accordance with the reflection position is changed, and the output of the photosensor 7 based on this is changed, whereby the movable body 6 is changed.
Is detected in the X direction.

In the Y direction, the width in the X direction of the non-reflection surface 10B near both edges in the Y + and Y− directions is from the center to the edge in the Y direction within a predetermined dimension B from the edge. , The width gradually increases from the dimension C to the dimension D, and the width of the reflection surface 10A is gradually reduced. As for the area size B near the both end edges in the Y direction and the enlargement amount D in the X direction, optimal values are set according to the characteristics of the reflection plate 5 and the photosensor 7. 10A and non-reflective surface 10B
Constant width.

Next, the operation of the embodiment of the present invention will be described in detail with reference to FIGS.
The movable body 6 moves in the X direction in FIG. 1, whereby the position at which the sensor beam 9 emitted from the photo sensor 8 is irradiated on the reflector 5 changes. Of the sensor beam 9 illuminated on the reflection plate 5, only the one that hits the reflection surface 10A of the reflection pattern is reflected and enters the light receiving portion of the photo sensor 8.

FIG. 3 shows a case where the movable body 6 is not displaced particularly in the Y direction and the sensor beam 9 hits near the center of the reflector 5 in the Y direction. FIG. 4 shows a case where the movable body 6 is displaced in the Y direction. The case where the sensor beam 9 hits near the edge of the reflection plate 5 is shown. FIGS. 3A and 4A are side views showing the relationship between the movable body 5 and the photosensor 8, and FIGS.
It is the IIIb-IIIb arrow view and IVb-IVb arrow view of the figure. Reference numeral 22 in FIGS. 3 and 4 indicates a sensor beam irradiation area on the reflection pattern.

In the case of FIG. 3, the sensor beam 9 is applied to the center of the reflecting plate 5 in the Y direction, and the reflected light is reflected on the reflecting surface 1.
The light returns to the photo sensor 7 as return light according to the ratio in the central region of 0A. Next, when the movable body 6 moves toward the end in the Y direction, the sensor beam irradiation area 22 on the reflection pattern
Moves as shown in FIG. 4 and the sensor beam irradiation area 22 approaches the vicinity of the edge of the reflector, which causes irregular reflection and the like at the edge of the reflector, and the reflected light increases as compared with the case of FIG. Since the X-direction width of the non-reflective surface 10B is gradually increased, the light reflected by the reflective surface 10A is:
As compared with FIG. 2, the increase in the amount of reflected light due to irregular reflection near the edge and the decrease in the amount of reflected light due to the decrease in the ratio of the reflection surface cancel each other, so that the final amount of reflected light is almost as shown in FIG. Stable output is possible without change. As can be seen from FIG. 5, the output fluctuation when the movable body is displaced in the Y direction is reduced as compared with the conventional example in FIG. 8, and as a result, stable displacement detection in the X direction becomes possible.

In the above embodiment, the case where the width of the reflecting surface 10A in the X direction is gradually reduced near the edge of the reflecting plate 5 is described. The width of the reflecting surface 10A in the X direction is gradually increased near the edge of the plate 5.

[0020]

As described above, according to the present invention,
Even when the movable body is displaced in the Y direction, the fluctuation of the sensor output due to the displacement can be almost eliminated, and the sensor output can follow only the displacement in the X direction. Detection becomes possible. In addition, since the sensor output is stable even when the sensor beam hits the vicinity of the edge of the reflector in the Y direction, the width of the reflector in the Y direction can be shortened, and the reflector is not so much restricted by space restrictions. Can be. Also, the design change from the conventional
Since only the reflection surface width of the reflection plate is increased or decreased according to the combination characteristics of the reflection pattern and the photosensor, it is not necessary to newly design a complicated pattern, and the design and production of the reflection pattern become easy.

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating a configuration of a position detection device according to an embodiment of the present invention.

FIG. 2 is a front view of a reflection pattern of a reflection plate in the position detection device.

3A and 3B are explanatory diagrams of a case where a sensor beam of the position detection device hits near the center in the Y direction, where FIG. 3A is a side view showing a positional relationship between a movable body and a photo sensor, and FIG. It is a IIIb-IIIb arrow view.

FIGS. 4A and 4B are explanatory diagrams of a case where a sensor beam of the position detection device hits near an edge in the Y direction, where FIG. 4A is a side view showing a positional relationship between a movable body and a photosensor, and FIG. FIG. 4 is a view taken along the line IVb-IVb.

FIG. 5 is a characteristic diagram showing a relationship between a Y-direction displacement and a photosensor output obtained by the position detection device.

FIG. 6 is a perspective view showing a configuration of a conventional position detecting device.

FIG. 7 is a front view of a reflection pattern of a reflection plate in the conventional position detection device.

FIG. 8 is a characteristic diagram showing a relationship between a Y-direction displacement and a photosensor output obtained by the conventional position detecting device.

[Explanation of symbols]

 Reference Signs List 5 Reflector 6 Moving body 7 Photosensor 8 Fixed body 9 Sensor beam 10A Reflective surface 10B Non-reflective surface

Claims (3)

[Claims] 1. An X and Y direction which are orthogonal to each other
By attaching a reflector located in the XY plane to the movable body that moves in the direction, and irradiating the reflector with light and receiving return light from the reflector on the fixed body facing the reflector. A photosensor that generates an output according to the return light is attached, and a reflection pattern is formed on the reflection plate by alternately arranging strip-shaped reflection surfaces and non-reflection surfaces extending in the Y direction in the X direction. By gradually increasing or decreasing the width in the X direction of the reflection surface and the non-reflection surface of the reflection pattern in accordance with their arrangement position, the amount of light returning to the photosensor corresponding to the reflection position is changed, and the output change of the photosensor based on this is changed. In the position detecting device for detecting the position of the movable body in the X direction, the width in the X direction of each reflecting surface in the vicinity of the edge in the Y direction of the reflecting plate, gradually increases from the center in the Y direction to the edge or Decrease A position detecting device characterized in that the number is reduced. 2. The position according to claim 1, wherein the width in the X direction of each of the reflecting surfaces is constant in a predetermined range in the center in the Y direction, and is increased or decreased near both end edges outside the predetermined range. Detection device. 3. An output of the photosensor in the vicinity of the Y-direction edge of the reflection surface is determined by an increase / decrease ratio of the X-direction width in the vicinity of the Y-direction edge of each reflection surface. 3. The position detecting device according to claim 1, wherein the output is set to be substantially equal to the output.